By Franklin W. Dixon
In a single of the main harmful and interesting instances in their careers, Frank and Joe Hardy support their father examine a chain of mysterious vehicle injuries. all of the drivers had visible a signpost marked probability presently ahead of his coincidence. The younger detectives examine, merely to find that the signposts have vanished. The tried robbery of a mystery experimental motor and the abduction of a recognized race horse are a part of this exciting case, which proves to be as sinister because the signposts themselves.